JPH09279031A - Production of universal polydiorganosiloxane/silica mixture by using hydrolyzable polydiorganosiloxane surface modifier, mixture obtained thereby, and room-temperature-curing sealant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polydiorganosiloxane/silica mixture having excellent adhesiveness by mixing a modified silica filler obtained by heating a mixture comprising reinforcing silica and a surface modifier represented by a specified formula under agitation with a polydiorganosiloxane.

SOLUTION: A reinforcing silica filler having a surface area of 90-500m²/g is mixed with 0.1-0.5 pts.wt., per pts.wt. silica filler, surface modifier represented by the formula: R¹O(R₂SiO)_xR¹ [ R is methyl, ethyl, vinyl or the like; R¹ is methyl, ethyl or acetoxy; and x is 2-12] at 90-180°C, and the mixture is devolatilized to form a modified silica filler. Next, a polydiorganosiloxane having a viscosity of 0.1-400 Pa.s is added to the modified silica filler, and the resulting mixture is agitated for shorter than 10min to obtain a modified silica-polydiorganosiloxane mixture having a silica filler content of 25-40wt.%. This mixture is mixed with a cross-linking agent (e.g. methyltriacetoxysilane) and a curing catalyst (e.g. dibutyltin diacetate) to obtain a room-temperature- curing silicone sealant.

COPYRIGHT: (C)1997,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides a method for preparing a universal polydiorganosiloxane-silica mixture and a non-slump room temperature vulcanizable (RTV) silicone sealant obtained therefrom.

[0002]

2. Description of the Related Art RTV
Silicone sealants are used in the art for various adhesive and weather resistant applications. Many of these applications require a material consistency that is attached to the vertical shape in the uncured state and maintains that shape until curing begins. Such sealants are said to have non-slump property or non-sag property. If the sealant sags or flows from its original shape, the desired weather resistance or adhesion is not obtained.

A typical silicone sealant formulation is
It includes a silicone polymer, a curing agent such as a crosslinker or a combination of a crosslinking agent and a curing catalyst, and a filler such as a reinforcing silica filler or extendable filler. Reinforcing silicas, such as fumed silicas, provide reinforcing properties to the network of polymers; to impart thixotropic properties to the uncured composition; and to impart a relatively high tensile and tear strength to the cured product. ,used. It is generally known that the silica must be treated to provide a non-sag sealant composition. Without treatment, a slumping or sagging sealant composition may result.

One method of preparing non-slack silicone sealants is to first react the crosslinker with the silicon-bonded hydroxy end groups of the polydiorganosiloxane,
Next, the silica filler is added. When using this approach, the crosslinker is used in an amount sufficient to react with the hydroxy groups of the polydiorganosiloxane and the hydroxy groups of the silica. This approach provides the desired non-slack sealant composition, but the process is limited to one curable chemical, such as a sealant composition with an organotriacetoxysilane crosslinker or an organotrioximosilane crosslinker. To be done.

However, if this universal mixture can be prepared without a curing agent, ie a cross-linking agent and a curing catalyst, and if this mixture is for the preparation of various sealant compositions with different curing agent chemistries. The benefits are many if it can be used as a base. For example, one universal starting mixture means that only a slight modification of the continuous mixing device is required, and that switching from one sealant composition to another is easy to achieve. The required components in the inventory are reduced for this purpose, leaving the previously utilized equipment items available for other manufacturing processes. Also, the variability of the types of products made from only one starting material is advantageous in quickly responding to the demands of new customers.

In order for a universal mixture to be viable for the manufacture of sealant compositions, it should be stable over the period immediately after its preparation until the time the mixture is incorporated into the RTV silicone sealant composition. Is. By "stable" herein is meant that the composition is suitably used to formulate a sealant composition such that the resulting composition has a maximum slump of 0.51 cm (0) as defined by ASTM D 2202. .20 inches), preferably less.

It is desirable to prepare a non-sag, one-part, RTV silicone sealant composition from a universal mixture that avoids the well known silica-polymer interaction problems such as crepe hardening or structure formation during storage. It is generally believed that the pretreated reinforcing silica filler eliminates these silica-polymer interactions and provides a stable composition containing the polydiorganosiloxane and the reinforcing silica filler. However, the present inventors have
A stable, universal mixture of silica filler and polydiorganosiloxane is obtained when the siloxane polymer has a viscosity of 400 Pa · s or less at 25 ° C. using conventional pretreated reinforcing silica filler. The present inventors have found that there is nothing. In fact, commercially available pretreated silica fillers such as Ca
Bot Corporation, Tuscola, I
Cabot TS-61 available from llinois
0 (trademark) and Cabot TS-530 (trademark) are
Additional processing is required to make the mixture with long-term stability such that an acceptable sealant composition is produced over as long as one year. TS-610 is a fumed silica treated with dimethyldichlorosilane having a surface area of 120 (± 20) m ² / g, TS-530
Is a fumed silica treated with hexamethyldisilazane having a surface area of 200 (± 40) m ² / g.

[0008]

One embodiment of the present invention is a polydiorganosiloxane from a free-flowing, powdered, surface-modified, reinforcing silica-polydiorganosiloxane composition that includes: -Introduce a method of making a universal mixture of silica: (i) Surface area of 90-500 m ² / during mixing and heating
Reinforcing silica filler with a median aggregate-agglomerate particle size of less than 600 μm in g and the formula R′O (R ₂ SiO) _x R ′.
(Wherein R is methyl, ethyl, vinyl, 3,3,3-trifluoropropyl or phenyl, each R ′ is selected from the group consisting of a methyl group, an ethyl group and an acetyl group, and x is 2 to 12 And a surface modifier represented by the formula (1), to form a filler mixture in which 0.1 to 0.5 parts by weight of the surface modifier are present per 1 part by weight of the silica filler; (ii) The filler mixture is mixed at a temperature in the range of 90 ° C. to 180 ° C., the surface modifier is dispersed throughout the silica filler, and the median aggregate-agglomerate particle size of the filler mixture is the silica. Filler agglomerate-keeping the filler mixture in a fluidized powder state until it is less than the median agglomerate particle size, the mixing process lasting no more than 30 minutes, during which the filler mixture is removed from the filler mixture during the mixing process. Excluding volatiles; (iii) 5 measured viscosity at ℃ is 0.1~400Pa · s
Is slowly added to the modified silica filler obtained in step (ii) while mixing the polydiorganosiloxane which is less than 10 minutes after the modified silica filler obtained in step (ii) is obtained. Finish the addition, here
The amount of polydiorganosiloxane added is such that it provides 25 to 40 wt% silica filler, based on the total weight of said polydiorganosiloxane and modified silica filler; then (iv) a uniform, free-flowing reinforcing silica. Mixing until a polydiorganosiloxane composition is obtained, where
The total mixing time of steps (iii) and (iv) does not exceed 10 minutes; then (v) the homogeneous free-flowing silica-polydiorganosiloxane composition obtained in step (iv) above Massing until a tenacity mixture is obtained; and (vi) gradually mixing more polydiorganosiloxane to have a higher concentration of polydiorganosiloxane than the free-flowing silica-polydiorganosiloxane (iv). , Making a homogeneous mixture with a silica filler content of 8-20 wt%, based on the total weight of this mixture.

Another embodiment of the invention includes the following:
A method of making a polydiorganosiloxane-silica mixture from a free-flowing, powdered, surface-modified, reinforcing silica-polydiorganosiloxane composition is provided: (a) a surface area of 90-500 m ² / g Aggregate-Reinforcing silica filler having a median agglomerate particle size of less than 600 μm is heated to a temperature in the range of 90 ° C. to 180 ° C. to remove volatiles from the silica filler; then (b) this heated The reinforcing silica filler is mixed with the formula R'O (R ₂ SiO) _x R'where R is methyl, ethyl, vinyl, 3,3,3-trifluoropropyl or phenyl while mixing this. And each R ′ is selected from the group consisting of a methyl group, an ethyl group and an acetyl group, x
Is a value of 2 to 12) to form a filler mixture in which 0.1 to 0.5 parts by weight of surface modifier are present per part by weight of silica filler; and (C) The filler mixture is heated and mixed at a temperature in the range of 90 ° C. to 180 ° C., the diol is dispersed throughout the silica filler, and the median aggregate-agglomerate particle size of the filler mixture is Aggregate of the silica filler-Keeping the filler mixture in a fluidized state until it is smaller than the median particle size of the agglomerates, the mixing process not exceeding 30 minutes in duration, during which the filler mixture is mixed. The volatile matter is removed from the mixture to obtain a modified silica filler; (d) the viscosity measured at 25 ° C is 0.1 to 400 Pa · s
Is gradually added to the modified silica filler of step (c) with mixing, and the addition is completed within 10 minutes after the modified silica filler obtained as a result of step (c) is obtained. The polydiorganosiloxane is added in an amount of 2 based on the total weight of the polydiorganosiloxane and the modified silica filler.
5 to 40 wt% silica filler is provided; then (e) mixed until a uniform, free-flowing, powdery, surface-modified reinforcing silica-polydiorganosiloxane composition is obtained, where: The total mixing time of steps (d) and (e) does not exceed 10 minutes; (f) a uniform, free-flowing silica-polydiorganosiloxane composition (e) is lumped until a consistency mixture of the paste is obtained. And then (g) slowly mixing more polydiorganosiloxane to have a higher concentration of polydiorganosiloxane than the homogeneous, free-flowing silica-polydiorganosiloxane obtained in step (e). And make a homogeneous mixture with silica filler content of 8-20 wt% based on the total weight of this mixture. A.

The method of the present invention is a one-part, non-sagging R
A universal mixture of polydiorganosiloxane and reinforcing silica used to make a TV silicone sealant composition is prepared. In the process of combining a reinforcing silica filler with a silanol-terminated polydiorganosiloxane, if the reinforcing silica filler uses some process to modify the surface of the silica filler, it may be conveniently combined with a short-chain polydiorganosiloxane surface modifier. When combined well, a non-sagging silicone sealant is made from the universal blend of the present invention.

Short-chain polydiorganosiloxanes having silicon-bonded groups for the purposes of the present invention have the formula R'O (R ₂
SiO) _x R '(where R is methyl, ethyl, vinyl,
3,3,3-trifluoropropyl or phenyl, each R ′ is a methyl group, an ethyl group or an acetyl group, and x has a value of 2 to 12). A preferred surface modifier is a mixture of molecules, at least 50 wt% of which have an x of 6 or less. A surface modifier having an x value of less than 6 has an x value of 6
It gives a base mixture with a longer stable storage time than larger surface modifiers. Particularly useful surface modifiers are those mixtures of molecules in which x has a value of about 4 and R is methyl and R'is methyl or acetyl.

The reinforcing silica filler has a surface area of 90.
In to 500m ² / g, aggregates - median agglomerate particle size of 60
It is less than 0 μm. This agglomerate-agglomerate particle size is Coulter Particle Size A
analyzer Model No. LS130, Hia
Measured by leah, Florida. Many of these silica fillers are commercially available and are known, for example, fumed silica and precipitated silica. These silica fillers may be untreated or treated. Treated silica fillers are also well known in the art and are commercially available, for example as TS-610 and TS-530. Examples of the silica filler treatment include triorganosiloxy surface treatment by reaction with triorganochlorosilane, hexaorganodisiloxane or hexaorganodisilazane; other silanes such as dimethyldichlorosiloxane; or silicon-bonded hydroxyl. Surface treatment with various polydiorganosiloxanes terminated with radicals or silicon-bonded alkoxy groups.

The surface modifier and silica filler are combined during the mixing and heating in step (i). They are combined such that there is 0.1 to 0.5 parts by weight of surface modifier per 1 part by weight of silica filler. The amount of surface modifier used to make the most stable mixture, i.e., the modified silica filler that gives the one-part RTV silicone sealant composition with the longest storage time and still non-sagging, is based on silica loading. It has more than 0.25 part by weight of surface modifier per 1 part by weight of the material. The storage stability of this mixture and its ability to be incorporated into non-slack sealant compositions is related to the chain length of the surface modifier.
In both the universal mixture and sealant composition of the present invention, which are all substantially equal except for the surface modifier, the longer the chain length of the surface modifier, for example x is 12, the shorter the chain length is. Greater amounts of surface modifier are required to obtain equivalent storage stability and sag in the final sealant composition for the inventive mixtures than those obtained using surface modifiers. On the contrary, the shorter the chain length of the surface modifier, for example when x is 2-4, is the surface required to obtain an equivalent storage stability for the sag of the mixture according to the invention and the final sealant composition. The concentration of denaturant is low.

The mixture of surface modifier and silica filler is 90
Fluidized (stirred) at a temperature of ℃ to 180 ℃, preferably 150 ℃ to 180 ℃. The resulting filler mixture has a surface modifier dispersed throughout the silica filler, and the median aggregate-agglomerate particle size of the filler mixture is step (i).
Aggregate of the starting silica filler of i) -maintained in a fluidized powder state until smaller than the median aggregate particle size. This filler mixture is more flowable than the starting silica filler at this point in the process of the invention and can be referred to as "fluffier". With a more fluffy point,
A modified silica filler is obtained. At the time of this process, the density of the filler mixture, reduced 2-3 pounds per cubic foot (32~48kg / m ^3). This fluffy state is an indication that the surface modifier has been dispersed throughout the silica filler. The mixing and heating steps to obtain the modified silica filler should not exceed 30 minutes. Preferably it is 5 minutes or less, more preferably less than 1 minute. During this mixing and heating step, volatiles are removed. This is accomplished with a partial vacuum, a nitrogen gas sweep or purge, or with a combination of both partial vacuum and nitrogen gas sweep. Above this 30 minute mixing and heating step, no benefit is seen. The rate of dispersion of the surface modifier in the silica filler is increased by the addition of a small amount of hexamethyldisilazane, such as less than 0.1 wt% based on the weight of the surface modifier.

Heating and mixing is accomplished in any mixing device that provides the necessary flow and agitation to maintain the surface modifier and silica filler in a constant fluid state, the required heating, and the removal of volatiles. To be done. One such mixer is
Littleford Bros. , Inc, Flor
Little obtained from ence, Kentucky
ford ^™ Flowshear mixer / gra
It is a nulator. This mixer provides the throwing and swirling action provided by a plow-shaped mixing tool. The blade of this plow rotates at 3600 rpm,
It is connected to a high speed compound shredding blade that introduces high impact and shear. This particular mixer provides the necessary mixing for the preparation of the modified silica filler of the present invention with the ability to be heated to remove volatiles. There is a window of mixing and heating times for the resulting modified silica filler to have excellent properties in order to provide a storage stable product in which it is used. For example, the universal mixture of the present invention, or a one-pack type R, which is obtained from the universal mixture and has no sag
TV silicone sealant composition. In this window of time, there is a relationship between the amount of surface modifier and temperature to give excellent properties. In the high temperature part of the above range, a relatively small amount of surface modifier is used to obtain the desired properties. In contrast, relatively low amounts of surface modifier are required to achieve the same excellent results in the lower temperature portion of this range. "Storage-stable" means that the products are used to make RTV silicone sealant compositions, starting at the time they are made and within the rheological property profile defined herein. It means that the properties of the RTV composition are maintained throughout the curing of the RTV composition.
It is desirable to retain uncured properties such as the rheology and non-sag morphology of our RTV silicone sealant compositions, as well as properties of the cured sealant such as tensile strength, elongation, modulus and tear strength.

The preferred method for making the modified silica filler is to heat the reinforcing silica filler to a temperature in the range of 90 ° C. to 180 ° C., and in step (a) water often combined with the silica filler. Excludes such volatiles. Volatiles are
It is removed by a partial vacuum, a sweep of nitrogen gas, or a combination of the two. This time is usually relatively short for this step due to the temperature used,
With the gas sweep, volatiles are easily removed in a minute or less. Preferably, this temperature is between 150 ° C and
It is 180 ° C. and the time is about 1 minute.

After the volatiles have been removed, heating and mixing is continued and the surface modifier is added in step (b), as defined above and in the amounts mentioned above. The period of heating and additional mixing is as described above. This filler mixture was added while maintaining it in a fluidized state until the surface modifier was dispersed throughout the silica filler and the particle size was observed to change as described in step (c) above. , 90
Heat to a temperature in the range of ℃ to 180 ℃, preferably 150 ℃ to 180 ℃. This mixing process has a duration of 30
Without exceeding minutes, the volatiles are removed as discussed above, yielding a modified silica filler. Preferably,
This mixing process has a duration of 30-60 seconds.
The steps (d), (e), (f) and (g) of the preferred process are steps (ii) as seen in the above description.
The same as i), (iv), (v) and (vi).

After preparing the modified silica filler, 2
A polydiorganosiloxane having a viscosity of 0.1-400 Pa · s measured at 5 ° C. is gradually added to the modified silica filler, the addition being less than 10 minutes, preferably 5
Allow to be completed in less than a minute (step iii). Sufficient polydiorganosiloxane is added to add a sufficient amount of polydiorganosiloxane to give a uniform, free-flowing powder having 25-40 wt% silica filler, based on the total weight of the powder. The modified silica filler and polydiorganosiloxane are then mixed until a uniform, free-flowing powder of polydiorganosiloxane and silica filler is obtained (step iv). The total mixing time in steps (iii) and (iv) is 1 to obtain a uniform, free-flowing, powdery, polydiorganosiloxane-silica filler composition.
Should not exceed 0 minutes. If the mixing time for steps (iii) and (iv) exceeds 10 minutes, the powder will agglomerate to form agglomerates that will not be exposed to the required degree of concentration of the powder and will be more concentrated when making the sealant composition. Brings in difficult processing conditions.

In step (iii), step (ii)
Polydiorganosiloxane is added incrementally to the modified silica filler obtained from
Can be added. Whether polydiorganosiloxane is added continuously at a gradual pace or in small portions,
There appears to be no significant change in properties except that the continuous and gradual pace of addition results in relatively easy processing to obtain the product.

The polydiorganosiloxane has a silicon-bonded hydroxyl group at both ends, and more than 50% of the polymer molecules have a silicon-bonded hydroxyl group at both ends and the remaining polymer molecules have a silicon-bonded hydroxyl group. It is selected from a mixture of polydiorganosiloxanes containing a group at one end and a triorganosiloxy unit at the other end. Polydiorganosiloxane, which is a mixture of polydiorganosiloxanes having silicon-bonded hydroxyl groups at both ends, and polydiorganosiloxanes having silicon-bonded hydroxyl groups at one end and triorganosiloxy units at the other end is described in U.S. Pat. Known in the art from 3274145, it teaches polydiorganosiloxane mixtures having both silicon-bonded hydroxyl groups and triorganosiloxy groups. For the present invention, when a polymer having both silicon-bonded hydroxyl groups and triorganosiloxy groups is used in step (iii), it is preferred that at least 80% are terminated with silicon-bonded hydroxyl groups. ing. The polydiorganosiloxane preferably has a viscosity at 25 ° C. of 5 to 100 Pa · s. This polydiorganosiloxane has the formula R " ₂ SiO
Including a diorganosiloxane unit represented by
R "is a monovalent hydrocarbon group or a halogenated monovalent hydrocarbon group, examples of which are alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, pentyl and hexyl; alkenyl groups such as vinyl, Allyl and hexenyl; cycloalkyl, such as cyclopentyl and cyclohexyl; aryl, such as phenyl and tolyl; and haloalkyl, such as chloropropyl,
There are trifluoropropyl and (2-perfluoropropyl) ethyl. Preferred polydiorganosiloxanes are those with mostly methyl groups and minor amounts of vinyl and phenyl groups. These polymers are defined as polydiorganosiloxanes, but in the presence of small amounts of other units often found in polydiorganosiloxanes as a result of the manufacturing process used, such as monoorganosilsesquioxane units, or SiO ₂ units. Good. A small amount is 5
It is meant that less than mol% of such units are present, preferably less than 2 mol% of such units.

Other types of polydiorganosiloxanes may also be used, such as hydrolyzable group-containing silicon units such as trimethoxysiloxy units, triethoxysiloxy units, methyldimethoxysiloxy units and methyldiethoxysiloxy units. Some have been terminated. These are described in US Reissue Patent No. 29760, which more completely describes such polyalkoxy-terminated polydiorganosiloxanes and their method of preparation. These polyalkoxy terminated polydiorganosiloxanes are represented by the formula:

[0022]

Embedded image

(Here, R ² is an aliphatic hydrocarbon group having 1 to 8 carbon atoms or a halogenated aliphatic hydrocarbon group,
R ³ and R ⁴ are each a monovalent hydrocarbon group having 1 to 18 carbon atoms or a monovalent halohydrocarbon group, n has an average value of 2 to 3, and y has an average value of 1.99 to 2 , Z has an average value of 1 to 1.01, and the sum of y and z is 3,
w is a value such that the viscosity at 25 ° C. is 0.1 to 400 Pa · s.

Some other polyalkoxy-terminated polydiorganosiloxanes have a divalent hydrocarbon linking group at the end of the polydiorganosiloxane, eg, US Pat. No. 3,175,993,4,871, 827 and 4,898,910. These patents show such polydiorganosiloxanes and methods for their preparation. These polydiorganosiloxanes are represented by the following formula.

[0025]

Embedded image

(Wherein R ⁵ is methyl, ethyl, propyl or butyl, and each R ⁶ is free of aliphatic unsaturation;
A monovalent hydrocarbon group or a monovalent halogenated hydrocarbon group, all having 1 to 18 carbon atoms, R ³ and w are as described above, and z is a divalent hydrocarbon group or a divalent hydrocarbon group. It is a combination of a hydrogen group and a siloxane group, and a is 0 or 1. Polydiorganosiloxanes having other silicon-bonded hydrolyzable groups at their ends are also useful, examples of such hydrolyzable groups include acetoxy and ketoximo groups.

After the product of step (iv) is obtained, it is massed (step v) until a mixture of paste consistency is obtained. This agglomeration process results in an amount of silica filler in the concentrate of 25
It is easily achieved in the range of ˜40 wt%, especially when the viscosity of the polydiorganosiloxane is lower than 50 Pa · s when measured at 25 ° C. This agglomeration process is performed at a relatively high concentration of silica filler, for example in the range of 35-40 wt%, especially when the viscosity of the polydiorganosiloxane is measured at 25 ° C.
When larger than a · s, a device having high shear force is required.

More polydiorganosiloxane is gradually mixed into the agglomerated product of step (iv),
8-20w based on the total weight of the universal mixture
It gives a universal mixture with t% silica filler. Preferably, the mixture comprises 8-15 wt% silica filler. If the concentration of the silica filler exceeds 15 wt%, the viscosity increases and the processing becomes more difficult.
Greater energy is required to make the sealant composition, as well as to make the mixture we claim initially. The concentration of polydiorganosiloxane in this mixture is higher than in the free-flowing silica-polydiorganosiloxane composition. The polydiorganosiloxane is preferably added and mixed under conditions which minimize formation of voids. This results in a faster preparation of the universal mixture according to the invention. When mixing a paste consistency material with a liquid material, such as polydiorganosiloxane, it is very easy to introduce voids from the gas atmosphere and special care is needed to keep the formation of such voids to a minimum. is there. Here and in addition US Reissue Patent No. 29,76
0; U.S. Pat. No. 3,175,993 and U.S. Pat.
Other types of polydiorganosiloxanes can be used, such as those terminated with hydrolyzable group-containing silicon units, such as the polyalkoxy-terminated polydiorganosiloxanes described in 4,871,827.

The universal mixture of the present invention
-"Stress" value is 700
Dyne / cm^TwoLarger, preferably 1000 dynes /
cm^TwoGreater than. This plateau stress is due to polymer / filler
It is a measure of interaction. Initial preparation plus all storage
Plateau stress value is 700 dynes / cm after aging ^Two
When larger, the universal mixture of the present invention is stable
Is considered to be. Plateau stress is 1000 dynes /
cm^TwoA sealant composition made from a larger mixture,
Measured with ASTM D 2202 0.5 cm (0.2 cm
Or a flow having a lower flow rate.
To produce The mixture according to the invention also has a shear stress of 50,0.
00 dynes / cm^TwoAt 1000 Pa · s or less, preferably
Is a shear-reduced viscosity (shear-t) of 600 Pa · s or less.
has a hinted viscosity (however,
Here, the viscosity is measured at 25 ° C.). Hence the general
The mixture has a plateau stress of 700 dynes / cm^TwoGreater than
And the shear-reduced viscosity is 1000 Pa · s or less. Preferred
The new mixture has a plateau stress greater than 1000 and shear
The reduced viscosity is 600 Pa · s or less at 25 ° C.

Plateau stress values are for cones and plates
Te Carri-Med^TM Rheometer (Model C
SL 500). These plateau stress values
Uses a flow method to measure
Was. The cone is 0.5 ° and the diameter is 2 cm,
The gap between the plates is 13 μm (test piece thickness)
Was. The invention mixture is gently removed from the storage container.
Issued. Place a few g on the temperature controlled bottom plate (25 ° C)
Place it and then place this plate in relation to the cone above
The thickness of the sample was set to 13 μm. 1 test piece
Equilibrated for ~ 5 min to reach 25 ° C. Initial response
Power 100 dynes / cm^TwoWas applied to this test piece. Equilibration
After that, the shear stress is changed to a logarithmic stress sweep mode (logar
(ithmic stress sleep mode)
Then, 50,000 dynes / cm over 5 minutes^TwoIs achieved
Until the shear stress was increased. This was called the rising curve. one
50,000 dynes / cm^TwoIs reached, this stress
Was held for 30 seconds. The shear stress is 100 Da for 5 minutes.
In / cm^TwoReduced to This was called the descent curve. Said
Dyne / cm^TwoThe plateau stress expressed by is the shear stress on the descent curve.
Breaking speed 0.023 seconds ^-1Was the shear stress. Shearing
Reduced viscosity, shear stress is 50,000 dynes / cm^TwoNoto
The viscosity was measured.

The resulting universal mixture is used to make other silicone compositions that are non-sag, non-sag, especially one-part RTV silicone sealant compositions. Such sealant compositions are prepared by adding a cross-linking agent or a moisture-hydrolyzable cross-linkable silicone compound containing a cross-linking agent and a curing catalyst (as a curing agent). Special crosslinkers can affect the non-sagging properties of the final RTV silicone sealant composition. The curing catalyst is optionally a one-part, RTV silicone sealant composition made using the universal mixture of the present invention,
Used to provide curing utility.

The cross-linking agent is a silicon compound having a silicon-bonded hydrolyzable group, preferably a silane. Examples of this silicon-bonded hydrolyzable group are acyloxy groups such as acetoxy, octanoyloxy and benzoyloxy; ketoximo groups such as dimethylketoximo, methylethylketoximo, methylamylketoximo, methylisobutylketoximo and Diethyl ketoximo; alkoxy groups such as methoxy, ethoxy and propoxy; alkenyloxy groups such as isopropenyloxy and 1-ethyl-2-methylvinyloxy; amino groups such as dimethylamino, diethylamino, butylamino and cyclohexylamino; aminoxy groups , For example dimethylaminoxy; and amide groups such as N-methylacetamide, N-ethylacetamide and N-methylbenzamide. These crosslinkers are 1
It is possible to have 3 or more silicon-bonded hydrolyzable groups per molecule. This cross-linking agent is silane,
When the silane has three silicon-bonded hydrolyzable groups per molecule, the fourth group is a non-hydrolyzable silicon-bonded organic group. Examples of said silicon-bonded organic groups are alkyl groups such as methyl, ethyl, propyl and butyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; There are aralkyl groups such as 2-phenylethyl; and groups obtained by substituting all or part of the hydrogen atoms in the above organic groups with halogen. A preferred silicon-bonded organic group is methyl.

The crosslinker can be a silane or a siloxane,
For siloxanes, the molecular structure can be linear, branched or cyclic. Examples of the silicon-bonded hydrolyzable groups include acyloxy groups such as acetoxy, octanoyloxy and benzoyloxy; ketoximo groups such as dimethylketoximo, methylethylketoximo, methylamylketoximo, methylisobutylketoximo and Diethyl ketoximo; alkoxy groups such as methoxy, ethoxy and propoxy; alkenyloxy groups such as isopropenyloxy and 1-ethyl-2-methylvinyloxy; amino groups such as dimethylamino, diethylamino, butylamino and cyclohexylamino;
There are aminoxy groups such as dimethylaminoxy; and amide groups such as N-methylacetamide, N-ethylacetamide and N-methylbenzamide.

Examples of the above-mentioned silanes and siloxanes include methyl-trimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, methylphenyldimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane and methyl. Triacetoxysilane, ethyltriacetoxysilane, vinyltriacetoxysilane, phenyltripropionoxysilane, ethyltris (N, N-diethylamino) silane, vinyltris (N
-Methyl-N-cyclohexylamino) silane, dimethylbis (N, N-dibutylamino) silane, methyltris (N-methylacetamido) silane, methylvinyl-
Bis (N-ethylacetamido) silane, vinyltris (N-ethylacetamido) silane, methyltris (N, N-diethylaminoxy) silane, phenyltris (N, N-diethylaminoxy) silane, methyltris (methylethylketoximo) silane, vinyltris (Methylethylketoximo) silane, 3,3,3-trifluoropropyltris (methylethylketoximo) silane, methyltris (isopropenoxy) silane, vinyltris (isopropenoxy) silane, ethylpolysilicate, n-propylortho-silicate, dimethyltetraacetoxy Disiloxane, pentamethyltris (N, N-diethylaminoxy) cyclotetrasiloxane, hexamethylbis (N, N-diethylaminoxy)
There are cyclotetrasiloxanes and mixtures thereof.

Some of the crosslinkers include triketoximosilane and tetraketoximosilane, triacetoxysilane and other triacyloxysilanes, trialkoxysilanes and tetraalkoxysilanes, and mixtures of ketoximo and alkoxy groups, and various The silane may have 0 to 4 ketoximo groups per molecule and 0 to 4 alkoxy groups per molecule, and the total number of alkoxy groups and ketoximo groups per molecule may be 3 or 4. Silanes having a silicon-bonded ketoximo group and an alkoxy group in the same molecule are described in US Pat.
Known from 7,967 and 4,973,623. The tribenzamidosilane crosslinker is a one-part, RT solution of the present invention.
5 is an example of another crosslinker that can be used to make the V silicone sealant composition. These are examples of crosslinkers that can be used to make non-slack RTV silicone sealant compositions.

The cure catalyst for a particular RTV silicone sealant composition depends on the cure rate required. Most RTV silicone sealant compositions containing oximosilanes or acetoxysilanes use tin catalysts for curing, especially diorganotin dicarboxylate compounds such as dibutyltin dilaurate, dibutyltin diacetate and dibutyltin bis-neodecanoate. For alkoxysilane crosslinkers containing RTV silicone silicone compositions, the most preferred cure catalysts are titanium catalysts such as tetrabutyl titanate, tetraisopropyl titanate, diisopropylbis (acetylacetonyl) titanate and diisopropylbis (ethylacetoacetonyl). ) Titanate. Such crosslinkers and cure catalysts are well known to those skilled in silicone sealants and are well known in the silicone sealant art. Therefore, a typical one-part, RTV silicone sealant, according to the present invention, is made from a universal mixture, crosslinker, cure catalyst, and other types of ingredients known to be used in silicone sealants, For example, fillers, pigments, fungicides, antioxidants, UV absorbers and other additives may be included.

The RTV silicone sealant composition of the present invention is made from a non-sagging, universal mixture. If the base mixture is cooled, ie kept below 15 ° C., the storage period can be extended. However, if conventional treated silica fillers are used to make the universal blends of the present invention, one-part RTV silicone sealant compositions will be prepared that do not result in non-sag products. If a surface modifier is used and the process defined by the present invention is used, a commercially available pretreated silica such as TS-610 and TS-530 may be used to provide non-sag A silicone sealant composition is made. In addition to obtaining a non-sagging one-part RTV silicone sealant composition from the claimed universal mixture, the resulting sealant composition has better transparency and better adhesion to plastics. One advantage of making a non-slack silicone sealant composition from the mixtures of the present invention is from one cure chemistry, such as the condensation reaction of silicon-bonded acetoxy functional groups, to another cure chemistry, such as silicon-bonded ketoximo. It is possible to change to a condensation reaction of a functional group. To date, altering the curing reaction has often created large amounts of waste material and long non-productive periods. However, with the present invention, switching from one curing reaction to another is rapid and the amount of waste is low. The flexibility to change quickly and without loss of material or time is a great advantage. An important aspect of our process is the surprisingly short time from the start of the production of the modified silica filler to the finished one-part RTV silicone sealant composition, with an overall time of less than 15 minutes. You can do it. This is a substantial time reduction relative to conventional manufacturing processes for making silicone sealants by including silica modification in the processing time calculations.

[0038]

The following example is presented for purposes of illustration and outlines the claims. In the following examples, “part” is based on weight, viscosity is measured at 25 ° C. unless otherwise specified, and Me is a methyl group.

Example 1 In preparing a universal mixture, 0.26 part of α, ω-diacetoxy (octa) as a surface modifier per part of reinforcing silica filler having a BET surface area of 200 m ² / g. Methyl tetrasiloxane) was mixed at room temperature. After mixing the surface modifier and the silica filler, the mixture was heated at 95 ° C. for 30 minutes to obtain a surface-modified silica filler. Viscosity is 16 Pa · s
And 85% of the end groups are hydroxyl and 15% of the end groups are trimethylsilyl units, sufficient polydimethylsiloxane (hereinafter referred to as polymer A. US Pat.
O.3274145) was mixed with the surface modified silica filler obtained above to give a polydimethylsiloxane-silica powder with 32 wt% silica filler. 95 parts of this mixture was mixed with 99.5 wt% of cross-linking agent (44 wt% of methyltriacetoxysilane, 49 wt.
% Ethyltriacetoxysilane, consisting of 7 wt% impurities) and 5 parts of a crosslinker mixture consisting of 0.5 wt% dibutyltin diacetate to prepare a one-part room temperature curable silicone sealant.

ASTM D 2 as one test process
The slump value using 202
Was measured. Extrusion speed was measured using ASTM C 603 except that the test sealant was extruded at a pressure of 620.5 kPa through a nozzle having a 0.3175 cm orifice. A sample of the sealant composition was spread to a thickness of 0.20 to 0.23 cm, and whether or not skin was formed on the surface of the sample was measured by lightly touching it with a finger, and the skin was expressed in minutes. Over-time (SOT) was measured. The SOT was the period in minutes from the initial spreading of the sample until the sealant composition did not stick to the finger and the sample surface was lightly touched by the finger. The tack free time (TFT) measured in minutes
It was measured according to the TMC 679 test procedure. Plateau stress was measured as defined above.

The following properties were measured after storing the sealant composition in a container sealed from atmospheric moisture for 8 days: Plateau stress = 1315 dynes / cm ² Extrusion rate = 296 g / min Slump = <0.254 cm (10 minutes later) SOT = 7 minutes TFT = 14 minutes

Example 2 Example 1 was repeated to produce the same surface modified silica filler. Sufficient Polymer A was mixed with the filler obtained above to give a polydimethylsiloxane-silica powder with 32 wt% silica filler. One mixture was then prepared by agglomerating this powder and gradually adding more polymer A to give 12 wt% silica filler. To 92.6 parts of this mixture was added 3.12 parts of the ketoximosilane mixture (70 wt%
Methyltri (methylethylketoximo) silane, 24
wt% methyldi (methylethylketoximo) silane,
0.5 wt% methyldimethoxy (methylethylketoximo) silane, consisting of 5.5 wt% impurities), 1.
By mixing 51 parts N-β-aminoethyl-γ-aminopropyltrimethoxysilane, 1.85 parts methylethylketoxime, 0.79 parts tetraethylorthosilicate and 0.15 parts dibutyltin dilaurate, 1 A liquid room temperature crosslinkable silicone sealant was prepared. Plateau stress, slump, extrusion rate, SOT and TFT were measured as described in Example 1.

The following properties were measured after 8 days of storage of the sealant composition in a container which was sealed from atmospheric moisture: Plateau stress = 4200 dynes / cm ² Extrusion speed = 290 g / min Slump = <0.254 cm (After 3 minutes) and 0.127 cm
(After 10 minutes) SOT = 3 minutes TFT = 9 minutes

 ─────────────────────────────────────────────────── ─── Continuation of front page (54) Title of the invention: Method for producing universal polydiorganosiloxane-silica mixture using hydrolyzable polydiorganosiloxane surface modifier, mixture obtained thereby and room temperature curing prepared therefrom Sex sealant

Claims (4)

[Claims] 1. A process for preparing a universal mixture of polydiorganosiloxane-silica from a free-flowing, powdery, surface-modified, reinforcing silica-polydiorganosiloxane, which comprises: (i) ) During mixing and heating, the surface area is 90-500 m ² /
Reinforcing silica filler with a median aggregate-agglomerate particle size of less than 600 μm in g and the formula R′O (R ₂ SiO) _x R ′.
(Wherein R is methyl, ethyl, vinyl, 3,3,3-trifluoropropyl or phenyl, each R ′ is selected from the group consisting of a methyl group, an ethyl group and an acetoxy group, and x is 2-12. Value)) to form a filler mixture in which 0.1 to 0.5 parts by weight of the surface modifier is present per 1 part by weight of the silica filler. (Ii) The filler mixture is mixed at a temperature in the range of 90 ° C. to 180 ° C., the surface modifier is dispersed throughout the silica filler, and the median aggregate-agglomerate particle size of the filler mixture is the silica filler. Agglomerate of material-Keeping the filler mixture in a flowing powder state until it is below the median agglomerate particle size, the mixing process does not exceed 30 minutes in duration and volatilizes from the filler mixture during the mixing process. Except for things Thus, a modified silica filler is obtained; (iii) the viscosity measured at 25 ° C is 0.1 to 400 Pa · s.
Is slowly added to the modified silica filler obtained in step (ii) while mixing the polydiorganosiloxane which is less than 10 minutes after the modified silica filler obtained in step (ii) is obtained. Finish the addition, here
The amount of polydiorganosiloxane added is such that it provides 25 to 40 wt% silica filler, based on the total weight of said polydiorganosiloxane and modified silica filler; then (iv) a uniform, free-flowing reinforcing silica. Mixing until a powder of polydiorganosiloxane is obtained, where
The total mixing time of steps (iii) and (iv) does not exceed 10 minutes; then (v) the homogeneous, free-flowing silica-polydiorganosiloxane obtained in step (iv) above is added to a consistency mixture of the paste. Until you get (mas
and (vi) gradually mixing more polydiorganosiloxane to have a higher concentration of polydiorganosiloxane than the free-flowing silica-polydiorganosiloxane (iv), the silica filler content being the Making a homogeneous mixture that is 8-20 wt% based on the total weight of. 2. The polydiorganosiloxane in step (iii) is incrementally added,
2. Addition to the modified silica filler of step (ii),
the method of. 3. Plateau stress
ess) of greater than 1000 dynes / cm ^{2 and} shear-thinned viscosit
y) is 600 at a shear stress of 50,000 dynes / cm ² .
A universal mixture obtainable by the process of claims 1 or 2 which is less than or equal to Pa · s, where the plateau stress and shear reduced viscosity are measured at 25 ° C. 4. A room temperature vulcanizable silicone sealant composition comprising the universal mixture of claim 3 and further comprising a moisture hydrolyzable crosslinkable silicone compound.